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Inelastic electron tunneling spectroscopy (IETS) performed with the scanning tunneling microscope (STM) has been deemed as the ultimate tool for identifying chemicals at the atomic scale. However, direct IETS-based chemical analysis remains difficult due to the selection rules that await a definite understanding. We present IETS simulations of single formate and benzoate species adsorbed in the same upright bridge geometry on a (111)-cleaved Cu surface. In agreement with measurements on a related substrate, the simulated IET-spectra of formate/Cu(111) clearly resolve one intense C-H stretching mode whatever the tip position in the vicinity of the molecular fragment. At variance, benzoate/Cu(111) has no detectable IET signal. The dissimilar IETS responses of chemically related molecules-formate and benzoate adsorbates-permit us to unveil another factor that complements the selection rules, namely the degree of the vacuum extension of the tunneling active states perturbed by the vibrations. As a consequence, the lack of a topmost dangling bond orbital is entirely detrimental for STM-based inelastic spectroscopy but not for STM elastic imaging. [ABSTRACT FROM AUTHOR]

We discuss how the excitation of high-frequency modes in adsorbed molecules may result in motion (e.g., rotation, translation, or dissociation) of the molecules. Our study is based on rate equations and considers one- and two-vibrational excitation processes, corresponding to linear and quadratic dependences of the reaction rate on the tunneling current in the case the scanning tunneling microscopy is used to excite the vibrations (inelastic tunneling). From the results reported in this paper it should be possible to obtain intramolecular transition rates directly from the experimental data, and gain some understanding on how these important quantities depend on the modes involved and on the substrate. [ABSTRACT FROM AUTHOR]

Presents a theoretical study of the electronic processes occurring in collisions of hydrogen molecular ions on an aluminum surface. Molecular dissociation induced by electronic transitions; Channels of the neutralization process; Auger deexcitation process of the b state; Efficient quenching of the excited state; Reduction in the molecular dissociation probability.

First-principles inelastic electron tunneling spectroscopy simulations give distinct signals for different phases of a water bilayer on a Pd (111) surface. Based on our recent electrochemical modeling of the water-Pd interface, we report on elastic and inelastic scanning tunneling microscopy simulations on two ice phases. Both phases exhibit only two tunneling-active optical phonons: the one corresponding to a stretching mode at higher frequency and the rocking/wagging one at lower frequency. However, the inelastic efficiencies at the phonon thresholds are very different between phases, enabling the discrimination of ice phases on metal surfaces.